I think it's fine for someone dealing with MI to be a therapist. I'm an engineer and am able to function fine at work. Not that it's equivalent, but in some sense a job is a job. You get up, go to work, do what you have to, and go home. Sure it's more difficult some days than others, but as you learn the skill set and become familiar with the tools and techniques of therapy, then you have the ability to let the training take over and you put yourself into the role. In some sense we're all playing our part in the great act.